A pro-form is a type of function word or expression that stands in for (expresses the same content as) another word, phrase, clause or sentence where the meaning is recoverable from the context. They are used either to avoid repetitive expressions or in quantification (limiting the variables of a proposition).
Pro-forms are divided into several categories, according to which part of speech they substitute:
An interrogative pro-form is a pro-form that denotes the (unknown) item in question and may itself fall into any of the above categories.
One of the most salient features of many modern Indo-European languages is that relative pro-forms and interrogative pro-forms, as well as demonstrative pro-forms in some languages, have identical forms. Consider the two different functions of who in "Who's the criminal who did this?" and "Adam is the criminal who did this".
Most other language families do not have this ambiguity and neither do several ancient Indo-European languages. For example, Latin distinguishes the relative pro-forms from the interrogative pro-forms, while Ancient Greek[1] and Sanskrit distinguish between all three: relative, interrogative and demonstrative pro-forms.
L. L. Zamenhof, the inventor of Esperanto, called a table of systematic interrogative, demonstrative, and quantifier pro-forms and determiners in a language a table of correlatives, after the relative and demonstrative proforms, which function together as correlatives. The table of correlatives for English follows.
interrogative | demonstrative | quantifier | |||||||
---|---|---|---|---|---|---|---|---|---|
proximal | distal | existential | elective | universal | negative | alternative | |||
determiner | which what |
this (sg.) these (pl.) |
that (sg.) those (pl.) |
some | any whichever whichsoever |
every each all |
no | another | |
pronoun | human | who whom |
this (one) (sg.) these (ones) (pl.) |
that (one) (sg.) those (ones) (pl.) |
someone somebody |
anyone anybody whoever whomever whosoever whomsoever |
everyone everybody all |
no one nobody |
another someone else somebody else |
nonhuman | what | this (one) (sg.) these (ones) (pl.) |
that (one) (sg.) those (ones) (pl.) |
something | anything whatever whatsoever |
everything all |
nothing | something else | |
out of two (dual) | which | this one (sg.) these (ones) (pl.) |
that one (sg.) those (ones) (pl.) |
one | either whichever whichsoever |
both | neither | ||
out of many (plural) | some one |
any whichever whichsoever |
each all |
none | |||||
pro-adverb | location | where | here | there | somewhere | anywhere wherever wheresoever |
everywhere | nowhere | elsewhere |
source | whence wherefrom |
hence | thence thencefrom |
whenceever whencesoever |
nowhence | ||||
goal | whither whereto whereinto whereunto |
hither | thither | somewhither | anywhither whithersoever |
nowhither | |||
time | when | now | then | sometime | anytime whenever whensoever |
always everywhen |
never | ||
manner | how whereby |
thus hereby |
thereby | somehow | anyhow however howsoever |
everyway | noway noways nowise nohow (col.) |
otherwise | |
reason | why wherefore |
therefore |
Some languages may have more categories. See demonstrative.
Note that some categories are regular and some are not. They may be regular or irregular also depending on languages. The following chart shows comparison between English, French (irregular) and Japanese (regular):
interrogative | quantifier | ||
---|---|---|---|
existential | negative | ||
human | who qui dare |
someone quelqu'un dareka |
no one personne daremo |
nonhuman | what que nani |
something quelque chose nanika |
nothing rien nanimo |
location | where où doko |
somewhere quelque part dokoka |
nowhere nulle part dokomo |
(Note that "daremo", "nanimo" and "dokomo" are universal quantifiers with positive verbs.)
Some languages do not distinguish interrogative and indefinite pro-forms. In Mandarin, "Shéi yǒu wèntí?" means either "Who has a question?" or "Does anyone have a question?", depending on context.